Procedures used to hydrolyze plant polysaccharides to their monomeric components were compared and a high performance liquid chromatographic (HPLC) technique for the analysis of monosaccharides was developed. Procedures using sulfuric acid as the hydrolytic agent were superior compared to a procedure using trifluoroacetic acid. The HPLC technique, involving anion exchange chromatography and pulsed amperometric detection, resulted in superior separation and detection of the monosaccharides compared to current HPLC techniques employing refractive index. An anion exchange HPLC technique with pulsed amperometric detection for the analysis of galacturonate in pectin was developed. No significant differences between the HPLC technique and a standard colorimetric procedure, with regard to the quantity of galacturonate detected in various hydrolyzed pectin samples, was noted. Both in situ and in vivo nonfermentable fractions of oat hulls (OH) and cottonseed hulls (CSH) were isolated using ruminants and analyzed. All structural components, including neutral monosaccharides, alkali-labile phenolics and nitrobenzene oxidizable phenolics present in original byproduct material were present in the nonfermentable fractions. From nuclear magnetic resonance analyses, a change in cellulose crystallinity as a result of fermentation was not apparent. Based on changes which occurred as the byproducts were fermented, we concluded that lignin encrustation was a factor inhibiting the fermentation of both CSH and OH. Lignin-carbohydrate/phenolic-carbohydrate complexes were factors inhibiting OH fermentation. The degree of polymerization of cellulose as a factor affecting fiber fermentation by ruminants was studied. Using in vitro methodology, a significant improvement in rate of fermentation of wheat straw following alkaline hydrogen peroxide (AHP) treatment (treatment times of 1 h, 2 h or 3 h) was noted. Alkaline hydrogen peroxide had a quadratic effect on extent of fermentation of wheat straw and solka floc as affected by treatment time. The degree of polymerization (DP) of wheat straw was decreased 19% compared to the control, while no effect of solka floc DP was noted. The ability of AHP to improve wheat straw fermentation may, in part, result from the reduction in DP of cellulose caused by AHP.